ADM9240 (sensor)

Added by ALMICO on 11 jun 2001

The ADM9240 is a complete system hardware monitor for microprocessor-based systems. The device communicates with the system via a serial System Management Bus. The serial bus controller has two hardwired address lines for device selection (Pin 1 and Pin 2), a serial data line for reading and writing addresses and data (Pin 3), and an input line for the serial clock (Pin 4). All control and programming functions of the ADM9240 are performed over the serial bus. An on-chip analog-to-digital converter with six multiplexed analog inputs measures power supply voltages (+12 V, +5 V, +3.3 V, +2.5 V-Pins 15 to 18) and processor core voltages (+VCCP1 and +VCCP2—Pins 19 and 14). The ADC also accepts input from an on-chip bandgap temperature sensor that monitors system ambient temperature. Two count inputs (Pins 5 and 6) are provided for monitoring the speed of fans with tachometer outputs. To accommodate fans with different speeds and different tacho outputs, a divisor of 1, 2, 4 or 8 can be programmed into the counter. Five digital inputs (VID4 to VID0—Pins 20 to 24) read the processor Voltage ID code, while a chassis intrusion input (Pin 7) is provided to detect unauthorized tampering with theequipment. When the ADM9240 monitoring sequence is started, it cycles sequentially through the measurement of analog inputs and the temperature sensor, while at the same time the fan speed inputs are independently monitored. Measured values from these inputs are stored in value registers. The ADM9240 contains an on-chip, 8-bit digital-to-analog converter with an output range of zero to 1.25 V (Pin 11). This is typically used to implement a temperature-controlled fan by controlling the speed of a fan dependent upon the temperature measured by the on-chip temperature sensor. Testing of board level connectivity is simplified by providing a NAND tree test function. The AOUT (Pin 11) also doubles as a NAND test input, while Pin 1 doubles as a NAND tree output.